This invention concerns fixturing for the inspection of tire casings and more particularly fixturing for enabling the interior of tire casings to be inspected for manufacturing defects.
In the course of manufacturing tire casings, it is necessary to carry out inspections to insure that various defects, which may occur in the course of the manufacturing process, are not present in a given selected tire casing, for adequate quality control of the manufacturing process.
One such inspection procedure has involved a holographic analysis of the interior of the tire casing. This necessitates the illumination of the interior of the tire casing to enable the formation of a hologram on the interior surface of the tire casing, which allows detection of certain manufacturing defects in the casing. In the practice of this method, it is necessary that the tire casing bead portions be spread apart in order to properly dispose the casing interior for the illumination of the interior by the inspection apparatus and the spread-apart condition of the tire bead portion must of course be maintained as the inspection process is carried out. The prior art approach has been to successively displace portions of the tire casing bead portion and successively position props extending across the interior of the tire casing.
The spreading for large truck tires requires the use of a power-operated spreader in order to carry out this method.
There are several disadvantages to this approach in the context of optical type inspection methods, including the holographic process described. Firstly, the props extending across the interior of the tire casing in engagement with the tire bead obstructs the viewing of the tire casing interior since the inspection apparatus is positioned within the rim opening of the tire casing and scans successive sections of the interior of the tire casing with illuminating beams in order to form the hologram of the tire casing interior surface. The presence of the props thus shadows a portion of the tire interior casing enabling defects to go undetected in these regions.
Secondly, the localized stress patterns created by the engagement of each of the props with the tire casing beads have been found to affect the hologram so formed which makes more difficult the detection of certain types of manufacturing defects in the tire.
Finally, the procedure of successively placing the props is relatively time consuming since it involves the progressive spreading of the tire and placement of each prop about the circumference of the tire bead.
It is accordingly an object of the present invention to provide a tire spreading holding fixture in which the tire bead portions may be maintained in a spread-apart position without obstructing the interior of the tire casing when viewed from a point interior of the tire casing rim opening.
It is yet another object of the present invention to provide such a holding fixture in which the engagement pressure in holding the tire rim bead does not create a localized stress on the tire casing bead such as to enable effective holographic analysis.
It is yet another object of the present invention to provide a tire casing spreader which simplifies the spreading of the large size tire casings which require power-operated equipment to carry out.